Men's Reactions Peak at Age 39

Scientists asked 72 men, ranging in age from 23 to 80, to tap their index fingers as fast
as they could for 10 seconds. The researchers also did brain scans to measure in
each subject the amount of myelin — a fatty sheath of insulation that
coats nerve axons and allows for signaling bursts in our brains.

Both the tapping speed and the amount of myelin was found to decline "with an accelerating trajectory" after age 39.

Study leader George Bartzokis, professor of psychiatry at UCLA,
called the results "pretty striking" and said: "That may well be why,
besides achy joints and arthritis, even the fittest athletes retire and
all older people move slower than they did when they were younger."

The myelination of brain circuits was known to peak in middle age. Bartzokis and others have long argued that brain aging might be primarily related to the myelin breakdown.

Learning more about this decline in fine-motor-skills speed offers some hope for treating the aging brain.

"Since in healthy individuals brain myelin breakdown begins to occur
in middle age, there is a decades-long period during which therapeutic
interventions could alter the course of brain aging and possibly delay
age-driven degenerative brain disorders such as Alzheimer's," Bartzokis
said.

The findings are detailed in the online version of the journal Neurobiology of Aging.

Live Science Staff

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